I have uninstalled Lightroom from my CPU. I would like to remove the old .ircat libraries off my system. Then I would like to reinstall lightroom. I would like to import photos from my external hard drive into Lightroom, but I would prefer for the photos to continue to reside no the external. Can you help?
I wouldn't do that. You will loose your edits when you delete your catalog. Your edits are stored in your catalog, not with your files (exception: if you use the side car file option, edits are also stored in the side car).
Anyhow, before touching to your catalog, do a backup.
See also here: Photoshop Lightroom catalog FAQ